Start handling pattern types at the HIR -> Ty conversion boundary

Author: oli-obk

compiler/rustc_hir_analysis/messages.ftl

@@ -349,6 +349,8 @@ hir_analysis_pass_to_variadic_function = can't pass `{$ty}` to variadic function
     .suggestion = cast the value to `{$cast_ty}`
     .help = cast the value to `{$cast_ty}`
 
+hir_analysis_pattern_type_wild_pat = "wildcard patterns are not permitted for pattern types"
+    .label = "this type is the same as the inner type without a pattern"
 hir_analysis_placeholder_not_allowed_item_signatures = the placeholder `_` is not allowed within types on item signatures for {$kind}
     .label = not allowed in type signatures
 

compiler/rustc_hir_analysis/src/errors.rs

@@ -7,6 +7,8 @@ use rustc_errors::{
 use rustc_macros::{Diagnostic, LintDiagnostic, Subdiagnostic};
 use rustc_middle::ty::Ty;
 use rustc_span::{symbol::Ident, Span, Symbol};
+mod pattern_types;
+pub use pattern_types::*;
 
 #[derive(Diagnostic)]
 #[diag(hir_analysis_ambiguous_assoc_item)]

compiler/rustc_hir_analysis/src/errors/pattern_types.rs

@@ -0,0 +1,9 @@
+use rustc_macros::Diagnostic;
+use rustc_span::Span;
+
+#[derive(Diagnostic)]
+#[diag(hir_analysis_pattern_type_wild_pat)]
+pub struct WildPatTy {
+    #[primary_span]
+    pub span: Span,
+}

compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs

@@ -21,7 +21,7 @@ mod object_safety;
 
 use crate::bounds::Bounds;
 use crate::collect::HirPlaceholderCollector;
-use crate::errors::AmbiguousLifetimeBound;
+use crate::errors::{AmbiguousLifetimeBound, WildPatTy};
 use crate::hir_ty_lowering::errors::{prohibit_assoc_item_binding, GenericsArgsErrExtend};
 use crate::hir_ty_lowering::generics::{check_generic_arg_count, lower_generic_args};
 use crate::middle::resolve_bound_vars as rbv;
@@ -2195,7 +2195,15 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                 // handled specially and will not descend into this routine.
                 self.ty_infer(None, hir_ty.span)
             }
-            hir::TyKind::Pat(..) => span_bug!(ast_ty.span, "{ast_ty:#?}"),
+            hir::TyKind::Pat(_ty, pat) => match pat.kind {
+                hir::PatKind::Wild => {
+                    let err = tcx.dcx().emit_err(WildPatTy { span: pat.span });
+                    Ty::new_error(tcx, err)
+                }
+                hir::PatKind::Range(_, _, _) => Ty::new_misc_error(tcx),
+                hir::PatKind::Err(e) => Ty::new_error(tcx, e),
+                _ => span_bug!(pat.span, "unsupported pattern for pattern type: {pat:#?}"),
+            },
             hir::TyKind::Err(guar) => Ty::new_error(tcx, *guar),
         };
 

tests/ui/type/pattern_types/bad_pat.rs

@@ -1,5 +1,3 @@
-//@ compile-flags: -Zno-analysis
-
 #![feature(pattern_types)]
 #![feature(core_pattern_types)]
 #![feature(core_pattern_type)]
@@ -10,3 +8,7 @@ type NonNullU32_2 = pattern_type!(u32 is 1..=);
 //~^ ERROR: inclusive range with no end
 type Positive2 = pattern_type!(i32 is 0..=);
 //~^ ERROR: inclusive range with no end
+type Wild = pattern_type!(() is _);
+//~^ ERROR: wildcard patterns are not permitted for pattern types
+
+fn main() {}

tests/ui/type/pattern_types/bad_pat.stderr

@@ -1,19 +1,25 @@
 error[E0586]: inclusive range with no end
-  --> $DIR/bad_pat.rs:9:43
+  --> $DIR/bad_pat.rs:7:43
    |
 LL | type NonNullU32_2 = pattern_type!(u32 is 1..=);
    |                                           ^^^ help: use `..` instead
    |
    = note: inclusive ranges must be bounded at the end (`..=b` or `a..=b`)
 
 error[E0586]: inclusive range with no end
-  --> $DIR/bad_pat.rs:11:40
+  --> $DIR/bad_pat.rs:9:40
    |
 LL | type Positive2 = pattern_type!(i32 is 0..=);
    |                                        ^^^ help: use `..` instead
    |
    = note: inclusive ranges must be bounded at the end (`..=b` or `a..=b`)
 
-error: aborting due to 2 previous errors
+error: "wildcard patterns are not permitted for pattern types"
+  --> $DIR/bad_pat.rs:11:33
+   |
+LL | type Wild = pattern_type!(() is _);
+   |                                 ^
+
+error: aborting due to 3 previous errors
 
 For more information about this error, try `rustc --explain E0586`.